1. Field of the Invention
The subject invention relates to integrated circuit and hybrid microcircuit fabrication apparatus and more particularly to an improved automated apparatus for picking up integrated circuit chips or dies and placing them on a substrate in the course of a die bonding procedure.
2. Description of Related Art
Integrated circuits of very small size are presently handled in so called "waffle packs." Waffle packs are small rectangular trays having a matrix of ridges which typically define square openings wherein an integrated circuit chip or die resides. Such chips may be very small, on the order of 0.010 inch square. Some are so small that the eye can barely detect them.
Apparatus is known which employs automated steps in the transfer of an integrated circuit die or chip from a waffle pack to a substrate. In a subsequent operation, electrical leads are bonded to the die or chip. Since the die or chip is not likely to be properly aligned in the waffle pack, it is necessary to employ some technique of properly aligning the die or chip with respect to the substrate.
Known prior art apparatus uses die squaring fingers or a separate alignment stage in the course of aligning the die or chip. Such systems neither advertise nor guarantee handling of a die smaller than 0.025 mil square. In addition, the separate alignment stage approach requires multiple die handling operations.
Another prior art device, a model 2500 Die Bonder system, manufactured by Hughes Aircraft Company, employs a "chalice" on which a waffle pack is placed under scrutiny of a television camera. The chalice is manually rotated until a selected die under examination aligns with cross hairs on a television monitor viewed by the operator. A mechanical arm is then automatically extended, and a collet with a vacuum needle picks up the die through suction. In this apparatus, a number of collets are rotatably mounted on a ratchet head, which is manually turned to select a needle opening size appropriate to the die being picked up.
The prior art has lacked the capability to automatically rotate a die during transfer from a waffle pack to a substrate. The prior art has also lacked the capability to pick up, rotate, and place a 0.010 inch square .times.0.005 inch thick die without damage. Without rotation capability, fully automatic operation of the die bonder system and integration of the system into a robotic system is impossible.
It has been further suggested that rotation of the chip or die could not be incorporated into an embodiment employing a mechanical arm which is extended to pick and place the die or chip. A rationale for such a view is that the dynamics of the arm would be too sensitive to mass, which would have to be increased in such an embodiment. Another concern has been that the increased mass might lead to breakage of the chips.
In addition, in pick and place apparatus, sensing must be provided to determine whether the apparatus has in fact picked up a die. Without such sensing, the collet needle tip can inadvertently be plunged into epoxy on the substrate. Prior art pick and place arms employ a vacuum sensor for this purpose.
Thus, addition of a die rotation capability must also take into consideration and provide proper pickup sensing. It has not been apparent that accurate vacuum pickup sensing can be provided in a system with die rotation capability because of potential sealing problems created by mechanical rotation of parts.
Finally, in addition to the foregoing obstacles, it has appeared desirable to maintain a pick and place accuracy of .+-.0.001 inches in any such apparatus employing a pick and rotate feature.